Option to donate to support development

[karlicoss]

Obviously it's early days, but Orgzly is such an essential app for me, and maintaining an open source project (especially for android) is a lot of work.
I'd be very happy to set up a recurrent donation to support the development, I'm sure there will be lots of other people as well.
If the maintainer(s) don't need money, I could donate to some other projects/causes they care about, so perhaps worth setting some channels up and adding to the readme later!